Researchers have continually attempted to increase the storage density and reduce the cost of data storage devices such as magnetic hard-drives, optical drives, and dynamic random access memory (DRAM). Recently, semiconductor-based electron sources have been developed that can be used in storage devices and which may avoid the difficulties noted above. An example of such a data storage device is described in U.S. Pat. No. 5,557,596. The device described in that patent includes multiple electron emitters having electron emission surfaces that face a storage medium. During write operations, the electron sources bombard the storage medium with relatively high intensity electron beams. During read operations, the electron sources bombard the storage medium with relatively low intensity electron beams. Such a device provides advantageous results. For instance, the size of storage bits in such devices may be reduced by decreasing the electron beam diameter, thereby increasing storage density and capacity and decreasing storage cost.
During fabrication, various contaminants from the ambient air can form on the electron emission surfaces of the data storage device. Such contaminants include various materials containing oxygen, nitrogen, and/or carbon. Perhaps most problematic of these is carbonaceous materials such as hydrocarbons. The formation of contaminants is disadvantageous in that their presence adversely affects operation of the electron emitters. For instance, the presence of contaminants increases electron scattering. In addition, where the electron emitters comprise field (i.e., tip) emitters, the work function of the emitters can be decreased, lowering the potential needed to emit electron beams from the emitters and thereby raising the currents substantially. This phenomenon makes it more difficult to control operation of the emitters in that the magnitude of the electron beams emitted from the emitters may be greater than desired, therefore increasing the opportunity for misreading and/or miswriting to a storage medium of the device. Removing these contaminants from the atmosphere to prevent their deposition on the electron emission surfaces during fabrication is difficult, if not impossible.
In addition to contaminants present in the ambient air during fabrication, further contaminants can be deposited on the emission surfaces of the electron emitters. For example, if the storage medium of the device is partially decomposed, or if contaminants on the surface are desorbed, during read and/or write operations, volatile components can be released that will settle on the electron emission surfaces. Like the airborne contaminants referenced above, these contaminants can similarly result in electron scattering and may significantly change emitter operational characteristics.
From the foregoing, it can be appreciated that it would be desirable to have a data storage device that employs a mechanism to remove contaminants from the emission surfaces of the electron emitters contained within the device.